The synthesis of iodobenzene starting from benzene and iodine is usually carried out in a liquid phase, in the presence of an oxidative agent; preferably the oxidative action is carried out by nitric acid (see Japanese Pat. No. 58/77830, U.S.S.R. Pat. No. 453392 and an article of Datta R. L. and Chatterjee N. R. on the J. Am. Chem. Soc., 39, 437, 1917). Other oxidative agents may be also used as well; none of them, however, has proved, hitherto, to be more efficient and convenient. For instance, iodic acid, sulphur trioxide and hydrogen peroxide were used (see Butler A. R.: J. Chem. Educ. 36, 508, 1971) and the iodination catalyzed by metal halogenides was reported as well (see Uemura A., Onoe A., Okano M., Bull. Chem. Soc. Jpn. 47, 147, 1974). Japanese patent publication No. 82/77631 teaches the direct iodination of benzene in the gaseous phase and in the presence of 13 X zeolites, but excludes absolutely the need of adding O.sub.2 or any other oxidizing agent. Recently, Italian patent publication No. 19860 A/84, in the name of the Applicant, describes a process for the synthesis of aromatic iodo-substituted compounds starting from alkaline salts of aromatic acids, by reaction with iodine. In all the well known methods, the selectivities to iodine are never higher than 90%; in a few methods use is made of expensive oxidative agents and in other methods one starts from not very available reactants. Now we have found that the synthesis of iodobenzene can be carried out more conveniently accordingly to the reaction: EQU 2C.sub.6 H.sub.6 +I.sub.2 +1/2O.sub.2 .fwdarw.2C.sub.6 H.sub.5 I+H.sub.2 O
(I)
using O.sub.2 as oxidative agent and a particular zeolite as catalyst.